Grading prostate cancer

The grade is a description of how the cancer cells look and act compared to normal cells. Knowing the grade gives your healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread. This helps them plan your treatment. The grade can also help the healthcare team predict your prognosis (the outcome) and how the cancer might respond to treatment.

Gleason classification system

The Gleason classification system is most often used to grade prostate cancer. It is used for adenocarcinoma, which is the most common type of prostate cancer. The Gleason classification system looks at the differentiation of cancer cells and the pattern (arrangement) of the cancer cells in the prostate. Differentiation describes how different the cancer cells are.

Gleason patterns and grade

To find out the grade of prostate cancer, the pathologist looks at tissue samples from the prostate under a microscope.

There are 5 patterns of prostate cancer cells based on their differentiation. The lower the pattern number, the more cancer cells look, act and are arranged like normal cells. Gleason patterns 1 and 2 are not commonly used because these cells look a lot like normal cells. The pathologist will give a grade for each pattern of prostate cancer cells found in the biopsy. The grade of the cancer corresponds to the pattern number. Most prostate cancers have a Gleason pattern of 3, 4 or 5.

Calculating the Gleason score

If the pathologist sees only 2 patterns of cancer cells, they will add the grades for each pattern together to get the total Gleason score. For example, if the pathologist gives the cancer cells in the most common pattern a grade of 3 and the cancer cells in the 2nd most common pattern a grade of 4, the total Gleason score is 7. This is often written on the pathology report as 3+4=7/10.

If there is a 3rd pattern in the biopsy samples, the grade of the most common pattern of cancer cells is added to the pattern with the highest grade. This may be the 2nd most common pattern or the least most common pattern. For example, if the pathologist gives the cancer cells in the most common pattern a grade of 3, and the cancer cells in the 2nd most common pattern a grade of 4 and another pattern of cancer cells has a grade of 5, the total Gleason score is 8.

Group grade

To make the Gleason score easier to understand, doctors have developed the Grade Group (GG) system. This gives a single score from 1 to 5 based on increasing Gleason scores. For example, GG 1 corresponds to a Gleason score 6 and GG 5 corresponds to Gleason score 9 or 10.

Gleason score descriptions

The Gleason score and Grade Group are described in the following table.

Group grade

Gleason score

Grade

Description

1

3+3=6

or less than 6

low

The cancer cells are well-differentiated, which means that they look, act and are arranged much like normal prostate cells. The glands in the prostate are seen.

The cancer is growing very slowly and often doesn’t need treatment.

2

3+4=7

low-intermediate

The cancer cells are moderately differentiated, which means they look different than normal cells but aren’t as abnormal as poorly differentiated or undifferentiated cells.

The cancer may grow very slowly and sometimes doesn’t need treatment.

3

4+3=7

high-intermediate

The cancer cells are moderately differentiated, which means they look different than normal cells but aren’t as abnormal as poorly differentiated or undifferentiated cells.

The cancer is growing at a moderate pace and usually needs to be treated.

4

4+4=8

high

The cancer cells are poorly differentiated. They look, act and are arranged very differently than normal prostate cells. The glands in the prostate can’t be seen or can’t be seen well.

The cancer is growing quickly and is more likely to spread.

5

9 or 10

very high

The cancer cells are undifferentiated. This means that they are very abnormal. They look, act and are arranged very differently than normal prostate cells. The glands in the prostate can’t be seen or can’t be seen well.

The cancer is growing very quickly and is more likely to spread. It has a poor prognosis.